The wear life of undoped and Ni-doped MoS2 was evaluated at application-relevant pressure and speed conditions in air. It is found that the Ni-doped coatings outperformed the undoped coatings, particularly at lower pressure (faster speed) conditions. To understand this, the evolution of the coatings during run-in was characterized in terms of wear track depth, material composition and microstructure. It is found that wear depth exceeds the thickness of the coatings after hundreds of cycles, in sharp contrast to the wear life that was measured to be tens of thousands of cycles based on friction. This suggests that sliding was facilitated by MoS2 continually worn from the sides of the wear track for most of the coating life. Further, microstructural analysis shows that the improved performance of Ni-doped coatings was attributable to cracking and delamination during the run-in stage, leading to more lubricious material available to facilitate sliding.

Nickel-titanium (NiTi) alloy is an attractive material for biomedical implant applications. In this study, the effects of laser shock peening (LSP) on the biocompatibility, corrosion resistance, ion release rate and hardness of NiTi were characterized. The cell culture study indicated that the LSP-treated NiTi samples had lower cytotoxicity and higher cell survival rate than the untreated samples. Specifically, the cell survival rate increased from 88 AE 1.3% to 93 AE 1.1% due to LSP treatment. LSP treatment was shown to significantly decrease the initial Ni ion release rate compared with that of the untreated samples. Electrochemical tests indicated that LSP improved the corrosion resistance of the NiTi alloy in simulated body fluid, with a decrease in the corrosion current density from 1.41 AE 0.20 μA/cm 2 to 0.67 AE 0.24 μA/cm 2 . Immersion tests showed that calcium deposition was significantly enhanced by LSP. In addition, the hardness of NiTi alloy increased from 226 AE 3 HV before LSP to 261 AE 3 HV after LSP. These results demonstrated that LSP is a promising surface modification method that can be used to improve the mechanical properties, corrosion resistance and biocompatibility of NiTi alloy for biomedical applications.

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